Acoustic phonon scattering by electron–hole droplets in Ge. II. Total scattering rate and anisotropy of scattering, as reflected in the shape of a droplet cloud

The pair‐phonon scattering rate is calculated for carriers inside an electron–hole drop in Ge. The calculation includes effects due to screening, electron mass anisotropy, and sound velocity anisotropy. The net scattering time is shorter by about a factor of two than found in previous calculations. A very similar integral occurs in calculating the force of the ‘phonon wind’ on the cloud of droplets. Using a simple model, this integral can explain the anisotropic shape of the cloud observed experimentally by Greenstein and Wolfe. The calculation accounts for both the broad lobes observed along 〈111〉 axes and the sharp flares along 〈100〉 axes (the latter due to a focusing of the phonons in Ge).